The concept of pulsed electromagnetic stimulation (PES) was first observed by the renowned scientist Michael Faraday in 1831. Faraday was able to demonstrate that time varying, or pulsed electromagnetic fields have the potential to induce current in a conductive object. Faraday's experimental setup was simple. He found that by passing strong electric current through a coil of wire he was able to produce pulsed electromagnetic stimuli. This pulsed electromagnetic stimulus was able to induce the flow of current in a nearby electrically conductive body.
In the years since the discoveries of Faraday, pulsed electromagnetic stimulators have found application in countless areas of scientific investigation. In 1965, the scientists Bickford and Freming demonstrated the use of electromagnetic stimulation to induce conduction within nerves of the face. Later, in 1982 Polson et al., U.S. Pat. No. 5,766,124 produced a device capable of stimulating peripheral nerves of the body. This device was able to stimulate peripheral nerves of the body sufficiently to cause muscle activity, recording the first evoked potentials from electromagnetic stimulation.
One of the earliest practical applications of electromagnetic stimulating technology took the form of a bone growth stimulator—a device that employed low frequency pulsed electromagnetic fields (PEMF) to stimulate bone repair. They first found use approximately 20 years ago in the treatment of non healing fractures, and are slowly becoming the standard of care for this condition.
As investigators have studied the effects of electromagnetic fields on fracture healing, it has been demonstrated that PEMFs can not only facilitate fracture healing but also promote numerous other positive effects on the human body, including: (1) causing muscles to contract, (2) altering nerve signal transmission to decrease experienced pain, and (3) causing new cell growth in cartilage. These powerful effects of pulsed electromagnetic stimulation have been well established in laboratory studies of animal models and also in multiple large, double blind, placebo controlled studies of human subjects published in the medical literature.
Erickson's U.S. Pat. No. 5,181,902, Jan. 26, 1993, which describes a device using a double transducer system with contoured, flat wound transducers intended to generate therapeutic flux-aided electromagnetic fields in the body. The device is suggested to be conformed to the contour of the patient's back and incorporates an adjustable belt into the design. This system, as it is described, is disadvantageous in at least two respects. First, the flat, wound nature of the coil in this device is limited in its delivery of pulsed electromagnetic fields to deep tissues of the body. Second, the rigid nature of this device, intended to provide bracing for patients recovering from spinal fusion surgeries, may prove uncomfortable to some patients, especially in delivering therapy to regions of the body other than the back, such as the knee, elbow, hand, or other joints and tissues.
U.S. Pat. No. 6,086,525, which discloses a device that has a single coil in the shape of a “C” where the intensity of the electromagnetic field is between the ends of the “C”. That point must be employed directly over the target nerve or muscle to be stimulated. The coil is toroidal in configuration and utilizes a unique core of vanadium permendur in the preferred form. One of the disadvantages of this device is that it requires a trained technician to treat the patient and to properly hand hold the open end of the “C” over the targeted nerve or muscle to be stimulated. The device is not portable and is designed for use in hospitals or similar institutions. Also the vanadium permendur core is required to increase the strength of the electromagnetic field to be strong enough to be effectively used. The design, shape and configuration described in Davey and other prior art devices, require the electromagnetic stimulator to be hand operated during use.
Tepper in U.S. Pat. No. 5,314,401, May 24, 1994 describes a pulsed electromagnetic field transducer that is intended to be conformable to the contour of a patients body. The PEMF transducer in this application is described as having a desired form and sufficient rigidity to maintain an anatomical contour. This system is disadvantageous in a number of respects. First, the desired contouring of this device will require that a significant number of different sizes be manufactured to accommodate the contours of an endless variety of body shapes. Second, the intended device does not incorporate markings to ensure that the device is placed in a correct alignment over the targeted area of the body. Finally, this proposed device utilizes flat, wound coils, providing PEMFs that do not penetrate as deeply or as uniformly into body tissues as those fields produced by solenoid coils.
In U.S. Pat. No. 6,179,770 B1, Jan. 30, 2001, Mould describes dual coil assemblies in a magnetic stimulator for neuro-muscular tissue, with cooling provided for the transducer coil. This device is intended to be held by a trained user over the targeted regions of the body in order to deliver PEMF therapy. The design of this device is limited by the difficult nature of manipulating a single coil and the cost-intensive requirement of using highly skilled medical personnel for operation.
Parker in U.S. Pat. No. 6,155,966, Dec. 5, 2000 describes a wearable article with a permanent magnet/electromagnet combination device to be used for toning tissue with focused, coherent EMF. This device is disadvantageous in several respects. First, this device is intended to be a hand-held application, with the user applying the device to targeted areas of the body. The hand-held nature of this application creates an inherently inconsistent and non-uniform method for delivery, especially difficult with the intention of the device to provide a focused electromagnetic stimulus. Second, the device combines a static magnet with the electromagnet assembly in an attempt to create a unipolar, negative polarity field. This form of electromagnetic field stimulation has not been demonstrated to be effective in the treatment of osteoarthritis, musculoskeletal pain, or atrophy treatment.
March's U.S. Pat. No. 6,200,259 B1, Mar. 13, 2001 describes a device with electromagnetic field coils applied front and back to a patient for treating cardiovascular disease by angiogenesis. An EMF dosage plan contemplates, multiple coil implants and pulse variables including carrier frequency, pulse shape, duty cycle, and total time exposed. This device describes the placement of coils around the regions of tissues in which collateralization of blood flow (or angiogenesis) is desired. The design contemplates applications including the use of coils embedded in a cloth wrap, which could be worn as a garment surrounding the body area of interest. Alternatively, an applicator with embedded coils to be placed around an arm or a leg to deliver the desired field is described. The use of PEMF in this application for the purpose of modulation of angiogenesis shows significant promise. The description of this device, however, does not suggest any extension of the electromagnetic phenomenon in circumstances where PEMF stimulation can provide dramatic opportunities for the treatment of osteoarthritis, and musculoskeletal pains including tendonitis, bursitis, and muscle spasms. Furthermore, this device is disadvantageous in the fact that it does not provide for the use of solenoid-type coils for the delivery of PEMF.
Poison's U.S. Pat. No. 5,766,124, Jun. 16, 1998 describes a magnetic stimulator of neuro-muscular tissue. A reserve capacitor providing more efficiency in the control circuitry is devised. The description of the device, however, describes the stimulating coil in broad, generic terms, and does not contemplate application of the coil in any type of body applicator or other specific method for delivering PEMF to targeted areas of the body. As a result, this device is disadvantageous, in the respect that is does not provide for any method or delivery system to provide consistent uniform PEMF stimulation.
Schweighofer's U.S. Pat. No. 6,123,658, Sep. 26, 2000 describes a magnetic stimulation device which consists of a stimulation coil, a high-voltage capacitor, and a controllable network part. This device is intended to differentiate itself from low-voltage, low current devices by using a specific high-voltage, high current design to deliver PEMF for the purpose of triggering action potentials in deep neuromuscular tissue. This coil in this device is described as having a difficult and expensive to use hand-held configuration.
Lin in U.S. Pat. No. 5,857,957, issued Jan. 12, 1999 teaches the use of functional magnetic stimulation for the purpose of inducing a cough function in a mammalian subject. The description of the device provides for the use of hand-held stimulation coil, intended to be placed over the anterior chest of the subject for the purpose of stimulating nerves to induce a cough. This system is disadvantageous in the requirement of hand-held delivery which is difficult and inconsistent. The description contemplates use of the device in the induction of cough, and does not contemplate extension of the use of the device into other areas of neuromuscular stimulation.
Tepper in U.S. Pat. No. 6,024,691, issued Feb. 15, 2000 describes a cervical collar with integral transducer for PEMF treatment. The description of this device provides for the use of a single coil transducer, formed into the shape of a cervical collar. This system is disadvantageous in several respects. First, this device does not provide for the use of solenoid-type coils in the delivery of PEMF, which can provide a uniform and consistent signal. Second, the semi-rigid design of the collar complicates the delivery of PEMF to persons of differing body sizes. That is, for a person with a larger than average (or smaller than average) size neck, the design and semi-rigid nature of the device would make an exacting fit difficult, thereby diminishing the effectiveness of any delivered therapy. Furthermore, this device is designed to immobilize the neck and is therefore not applicable to most patients. Lastly, the device must be lowered over the head making application difficult.
Erickson in U.S. Pat. No. 5,401,233, issued Mar. 28, 1995 describes a neck collar device for the delivery of PEMF therapy. The description of this device provides for the use of semi-rigid transducers, intended to be conformable to a selected anatomical contour. This device in disadvantageous in respects similar to those of Pollack U.S. Pat. No. 5,401,233, in that the device does not provide for the use of solenoid-type coils. Furthermore, this device, is intended to provide bracing (as might be necessary for the treatment of fractures or after surgery). As a result, the rigidity of the device necessary to serve the bracing function makes the device less comfortable to wear, especially for a person who would not require bracing (such as in the treatment of arthritis, muscle spasm, or other forms of musculoskeletal pain).
Kolt in U.S. Pat. No. 5,518,495, issued May 21, 1996 describes a coil wound on a large bobbin that permits the insertion of an arm or a leg into the field of the coil for PEMF type therapy. This device is disadvantageous in several respects. First, the described use of a bobbin, around which the wire for the stimulating coil is wound provides for the treatment of certain areas of the body, but is certainly limited in its ability to deliver therapy to areas of the body such as the hips, shoulder, back, neck, etc. That is, the constraints of our human anatomy make it nearly impossible to approximate a metal bobbin, and thus the stimulating coil, to regions of the body such as the ball and socket joints of the hip or shoulder, where the round metal bobbin would strike the torso before it allowed the stimulating coils to adequately blanket with therapy the arm and/or joint in the hip and shoulder. Similarly, the use of a metal bobbin for the delivery of PEMF stimulation to the back would necessitate a large, cumbersome delivery system (into which the entire body would have to fit) in order to adequately deliver stimulation to targeted areas on the back or torso. Second, the device is described as a rigid bobbin through which the extremity is placed. This format makes application more difficult in that the applicator cannot be worn and therefore does not provide for consistent ideal placement of the extremity to maximize field effects. In fact, most designs of a similar nature are clinic-based, devices and, therefore, would not be amenable to home healthcare applications as with the current invention. Third, the device described magnetic field within the bobbin is intended to have a maximum magnetic flux density in the range of 4.5 to 6 gauss. Studies (such as Trock et al in the Journal of Rheumatology 1994; 21(10): 1903-1911) have shown that PEMF stimulation in the range of 15-25 or more gauss are effective in the treatment of osteoarthritis or other musculoskeletal pain conditions.
Pollack in U.S. Pat. No. 5,014,699, issued May 14, 1991 describes a coil wound around the cast on an appendage for the delivery of PEMF treatment to fractured bone. The described device has shown promise for the treatment of fractured bone, especially nonunion or delayed healing fractures. However, the description of the device does not provide for extension of this application to the treatment of other conditions, such as arthritis, musculoskeletal pain, or atrophy.
Imran in US Pat App No 2006/0052839 filed Sep. 7, 2005 describe the use of an implantable stimulator for the treatment of chronic back pain. While this modality may be effective at treating back pain, it requires a major surgery and will eventually suffer from habituation as the area around the needle fibroses and the nerve becomes deadened to repeated stimulation.